1. Field of the Invention
The subject invention is generally related to a means and method for treating exhaust emissions from an internal combustion engine and is specifically directed to an exhaust gas combustor for igniting and burning untreated exhaust gases released from an internal combustion engine.
2. Description of the Prior Art
It is known to treat exhaust gases as they are released from an internal combustion engine. Typically, present day automobiles incorporate a catalytic convertor downstream of the exhaust for converting harmful emissions to less toxic, cleaner exhaust. Most vehicles now routinely incorporate catalytic conversion systems. In fact, catalytic converters are present on all automobiles now sold in the United States and significantly reduce tailpipe emissions of hydrocarbons, carbon monoxide and nitrous fumes.
While such systems have gained widespread acceptance for highway vehicles, similar suitable converter systems have not been developed for other internal combustion engines. This is particularly true for small engine applications, including both four-stroke and two-stroke designs. In reality, the emissions from such engines are more harmful to the atmosphere and environment than the emissions from highway vehicles since such engines generally run fuel rich, releasing larger concentrations of more toxic exhausts than the typical untreated exhaust of an automobile or truck. At the present time, catalytic converters have not gained widespread acceptance in such applications because of the incremental cost factor and, in some cases, the restricted space and weight requirements for small engine applications.
Further, while catalytic converters have greatly reduced harmful emissions in general, the converters do not operate efficiently until the exhaust gases reach a temperature range within the optimum operating range of the converter. This generally takes several minutes of operation after a cold start.
In fact, present day automobiles emit upwards of 80 percent of their total mass emissions during the first sixty seconds of operation when tested under the current EPA Federal Test Procedure. This is primarily due to a cold and therefore, ineffective catalytic converter. Typically, these catalysts must be at an operating temperature of approximately 300.degree. C. before they are effective at reducing emissions.
These problems have been well documented, and there have been numerous prior art attempts to either provide alternative emissions control or to further increase the efficiency of catalytic converters. One of the more popular methods of accelerating catalyst temperature is to electrically heat the catalyst substrate. However, this is inefficient and requires that the passenger wait before starting the vehicle so that the electrically heated catalyst can preheat. In addition, more equipment is generally required, such as an auxiliary battery and the like, further increasing the price penalty associated with incorporation of such systems.
Over the years, other systems have been developed for heating exhaust emissions to produce a cleaner exhaust. An early attempt is shown in U.S. Pat. No. 1,605,484, entitled: "Method of and Apparatus for Treating Exhaust Gases" issued to C E. Thompson, et al, on Nov. 2, 1926. As there shown, a secondary combustion is achieved under controlled conditions to further burn the untreated emissions from an internal combustion engine. A supplemental flame is utilized in a secondary chamber. An auxiliary battery supply is utilized to supply electrical ignition to the flame chamber. A secondary source of fuel may also be employed to enhance the secondary combustion cycle. Similar ideas are shown in U.S. Pat. Nos. 1,834,126; and 3,065,595. None of these devices have gained widespread acceptance because they have proven to be relatively inefficient, expensive to manufacture and operate, often requiring additional ignition circuits as well as secondary fuel delivery, and inordinate space requirements making them impractical to incorporate in typical automobiles.
More recently, U.S. Pat. No. 5,207,058, entitled: "Internal Combustion Engine" issued to S. Sasaki, et al, on May 4, 1993 discloses an exhaust purifying system for a direct injection engine, utilizing an ante-chamber in the exhaust tract. This system is only applicable to direct injection engines and the ante-chamber is not capable of sustaining combustion.
U.S. Pat. No. 5,263,318, entitled: "After-burner System" issued to N.Oota, et al, on Nov. 23, 1993 discloses a system incorporating hydrogen stored in a reforming tank and injected into the exhaust, requiring not only an extra injector but also a source of hydrogen, making it impractical for widespread application.
U.S. Pat. No. 5,277,025, entitled: "Exhaust Burner Control" issued to E. V. Gonze, et al, on Jan. 11, 1994, discloses a control system for an internal combustion exhaust gas heater and provides air and fuel to the heater in appropriate proportions to promote proper ignition. An external fuel injector is required and additional fuel is consumed during the burning cycle.
While numerous methods and apparatus have been disclosed directed toward the afterburning of internal combustion exhausts, none have gained acceptance because they either are impractical due to size or costs, or because they do not deal with cold starting issues, per se, and therefore, do not enhance the effects of the already accepted catalytic converter systems incorporated in many applications. Therefore, there remains a need for a practical method and apparatus for burning internal combustion exhaust to provide a rapid heating of the catalytic substrate to promote more efficient catalytic operation, particularly during cold start. In addition, there is a continuing need for an effective, inexpensive and unencumbering method and apparatus for treating the heretofore untreated exhausts of small engine applications.